An inorganic spheroidized particle is obtained by the method in which crushed raw material powder is melted in high-temperature flame and spheroidized by its surface tension. For example, highly-pure spheroidized silica that is obtained by using silica as a raw material is widely used as a filler for an epoxy-sealing material of a semiconductor device, and a lot of merits such as improved fluidity of a filler, high filling quantity, and improved abrasion resistance can be obtained by spheroidizing. In the present specification, an inorganic spheroidized particle may be simply described as a spheroidized particle.
As a prior art regarding the production of an inorganic spheroidized particle, there are the methods disclosed in Patent Documents 1 to 4. Because high-temperature flame is needed for the spheroidizing of raw material powder, a burner of an oxygen-gas combustion system is usually used.
Examples of the burner include a premixing type burner and a diffusion type burner. In a premixing type burner, oxygen and a combustion gas are preliminarily mixed and ejected to the combustion place. Meanwhile, in a diffusion type burner, oxygen and a combustion gas are separately ejected and mixed at the combustion place. Patent Document 2 discloses a premixing type burner, and Patent Documents 1, 3, and 4 disclose a diffusion type burner.
The diffusion type burner disclosed in Patent Document 1 has the concentric double pipe in which a lot of small pipes are provided between the inner pipe and the outer pipe. This burner is disposed in a vertical furnace, a silicon raw material is flowed down spontaneously (or with pressurization) through the central pipe (i.e. inner pipe) of the burner, and the raw material powder is supplied into flame made by a combustible gas from the small pipes and an oxygen gas from the outer pipe, to thereby produce a melted silica spheroidized body.
In the premixing type burner disclosed in Patent Document 2, raw material powder, oxygen, and LPG are sufficiently mixed, and the raw material powder is supplied into flame made at the end of the burner.
The diffusion type burners disclosed in Patent Documents 3 and 4 have the concentric quartet pipe structure in which raw material powder is supplied through the central pipe into the combustion chamber by using oxygen or an oxygen-enriched air as a carrier gas, a fuel gas is supplied through the outer circumference thereof, the primary oxygen and the secondary oxygen are supplied through the further outer circumference thereof, and cooling water path is provided around the most outer circumference, to thereby cool a burner.
In addition, Patent Documents 3 and 4 disclose the production apparatus that uses the diffusion type burner to produce inorganic spheroidized particles.
In the production apparatus of inorganic spheroidized particles disclosed in Patent Document 4, as illustrated in FIG. 3, raw material powder is cut off from the conventional raw material feeder A, and carried to the burner B with a carrier gas that is supplied through the line A′. Into the burner B, oxygen from the oxygen supplier C and a combustible gas from a LPG supplier D are supplied. The particles, which are spheroidized within flame in the vertical burner E, are subjected to the temperature dilution with the air introduced into the vertical burner E through the line F, and collected by the following cyclone G and bag filter H.    [Patent Document 1]    Japanese Unexamined Patent Application, First Publication No. Sho 58-145613    [Patent Document 2]    Japanese Unexamined Patent Application, First Publication No. Sho 62-241543    [Patent Document 3]    Japanese Patent No. 3331491    [Patent Document 4]    Japanese Patent No. 3312228